What is written on the back of the United States Declaration of Independence?

The 2004 movie "National Treasure" alleged (among other historically crazy things) that there is a secret map on the back of the Declaration of Independence. There is no map, but there is something on the back of the engrossed and signed parchment. A label at the bottom of the parchment reads, "Original Declaration of Independence dated 4th July 1776". This handwritten note gives a real clue into the history of the Declaration of Independence, which spent much of its early existence rolled up with other documents, under the care of Charles Thomson, Secretary of the Continental Congress. No one knows who wrote it, when, or why but it's thought that it was written before it was rolled up for storage.